机载多普勒频移的递推及相移检测

Recursion and Phase Shift Detection of Airborne Doppler Shift

在机载站飞行方向前方某一距离处的多普勒频移能够通过递推计算的方法由站点当前位置处的相位测量结果而被直接确定。首先,基于平面几何关系,由机载平台匀速运动时各个几何变量的运动特性导出了仅利用当前时刻的多普勒频移测量值和径向距离获得在虚拟飞行距离处多普勒频移递推值的计算式。然后,进一步直接利用相差测距、测向法求解递推式中所包含的径向距离和方位角,得到了仅基于相差检测的多普勒频移递推公式。且初步的误差分析表明,只要载机的飞行速度较低,虚拟基线的长度较短,所检测的信号波长较长,则递推频移的测量误差可控制在十几赫兹之内。

The Doppler shift at a certain position in front of the flight direction of airborne station can be directly determined by recurrence method and making use of the measurement result for phase difference at current position. Firstly, based on plane geometry, the recursion formula of Doppler shift at a virtual position in front of the flight direction of airborne station, which only uses the measured value for Doppler shift and radial distance at current position, can be derived according to the kinetic characteristic of geometric pa- rameters while airborne platform is in uniform motion. Then, using the ranging and direction finding method based on phase difference solves the radial distance and azimuth angle including in the recursion formula and obtains the Doppler recursion formula only based on phase difference detecting. The elementary error analysis shows that the measured errors can be limited in the range from 10 to 20 Hz in the case of low flight speed, short virtual baseline length, and long wavelength of measured signal.